This invention relates to a vacuum flask, particularly to an improved construction of a vacuum flask in which the flask is made of a non-fragile material.
It is known in the art to provide a vacuum flask which is made of glass for accomodating and insulating hot or cold liquid. Although such vacuum flask offers effective protection for hot or cold liquid, it is not durable due to the fragile characteristics of the glass. There are also plastic bottles which include foamed plastic insulating material for keeping the water warm. Such bottles are not as effective as the glass vacuum flask.